This invention relates to provision of new compositions of materials that have very low loss and relatively high dielectric permittivities at microwave frequencies.
An ideal solid state material for some microwave applications would have an associated loss, measured by the parameter tanxcex4, that is no larger than 0.001, would have an associated relative dielectric coefficient ∈rel that is 100-1000, and would have a resonance frequency that is tunable over a range of 50 percent or more of a central frequency. It is unlikely that a material having all these characteristics exists, although workers in this field continue to search for xe2x80x9cbest possiblexe2x80x9d materials, based on relaxed criteria. The combined criteria set forth in the preceding are stronger than are needed in some applications. What is needed is a group of materials that comply with less daunting requirements that still permit fabrication and practical use of such materials in real world environments.
These needs are met by the invention, which provides a group of materials in which electrical conductivity is suppressed, providing very low associated loss coefficients tanxcex4 and providing fairly high relative dielectric coefficients ∈. A general chemical composition for this group of materials is (BaySr1xe2x88x92y)(Ti1xe2x88x92xMx)O3, with 0xe2x89xa6xxe2x89xa61 and 0xe2x89xa6yxe2x89xa61, and M is a substance or mixture including one or more of the elements Ta, Zr, Hf, V, Nb, Mo, W, Mn, Sc, Re, Al, Gd and Cr. Preferably, one or more of the elements represented by the symbol M has a valence of at least 4 in at least one oxidization state. The material may include one or more additives drawn from a second group including Mg, Ca, Sc, Y, La, Ce, Al, Ga, Cr and Nd.